1. Field of the Invention
This invention relates to a liquid jet recording head which performs recording by discharging liquid for recording such as ink, etc. by utilizing heat energy to form its droplets and attaching the droplets onto a recording medium such as a paper, to a substrate for the head and to a liquid jet apparatus having the head.
2. Related Background Art
Recording head to be used for the liquid jet recording method which utilizes heat energy for formation of droplets to be discharged generally comprises a discharge opening for discharging liquid for recording such as ink, etc.; a liquid path communicated to the discharge opening having a portion at which heat energy to be utilized for discharging liquid acts on liquid and an electrothermal transducer which is a heat energy generating means for generating the heat energy having a heat-generating resistor and a pair of electrodes connected to the heat-generating resistor, and has, for example, a structure shown in a separated state in the schematic perspective views of FIG. 2.
Among the recording heads having such constitution for example, the recording head disclosed in Japanese Laid-open Patent Application No. 55-126462, as shown in FIG. 1, consisted of a heat-generating resistor 208 for generating heat energy on a surface of support, electrodes 209, 210 for supplying electrical signals thereto formed by lamination according to thin film forming technique, etc. to form a substrate 202 for recording head, and further a liquid path 204 in contact with the heat-generating portion 201 of the heat generating resistor 208 and a discharge opening 217 formed on the substrate.
One of the specific feature of the recording head resided in that no protective layer as seen in the prior art was laminated on at least the upper part of the heat-generating portion 201 of the heat-generating resistor 208, thus having a structure in which the heat energy generated by the heat-generating portion 201 of the heat-generating resistor 208 can be readily transmitted directly to the liquid in the liquid path 204.
If electrodes 209, 210 are made of a corrosion resistant material such as gold, it is not required to provide protective layer 213, 214 thereon, but when they are formed of a readily corrosive material such as Al, it is preferable that protective layers 213, 214 comprising an inorganic insulating material such as SiO.sub.2, SiN, etc. or a heat-resistant organic polymer such as polyimide, etc. as shown in the Figure at the portions other than the heat-generating portion 201 of the heat-generating resistor 208.
As the material for forming the heat-generating resistor 208 of the recording head of such constitution, there have been used in the art materials exhibiting appropriate resistance values, specifically, noble metals (elements of the group VIII, etc.), high melting transition elements (elements of the groups III, IV, V, VI, etc.), alloys of these, or nitrides, borides, silicides, carbides of oxides of these metals, and further silicon-diffused resistors, or amorphous films composed mainly of carbon, etc.
In the recording head of the constitution having no protective layer provided on the heat-generating resistor as described above, its durable life depends greatly on the performance of the heat-generating resistor.
Shortly speaking, since the heat-generating resistor layer is subject to heat for gasification of liquid, and cavitation shock created during droplet dischargigng and chemical action of liquid, it must be excellent in heat resistance, breaking resistance, liquid resistance, oxidation resistance, etc.
Whereas, no material for formation of heat-generating resistor satisfying all of these requirements has been known in the art.
For example, single substance metals of noble metals, high melting transition metals, etc. have generally low specific resistance to pose a problem in the point of heat-generating efficiency, while in nitrides, borides, silicides, carbides, oxides of the above metals, or silicon-diffused resistors, or amorphous films composed mainly of carbon etc., there is sometimes the drawback of weak resistance to mechanical shock by cavitation shock, which may be estimated to be due to the fact that the atomic bonds of such compounds are covalent bonding in nature.
Also, crystalline or polycrystalline alloys were sometimes insufficient in chemical stability.